<div>
  {{answer.displayed_question}}
  {% if answer.correct %}
  <div>
    <pre>{{answer.displayed_proof[0]}}</pre>
  </div>
  {% endif %}

  {% if not answer.correct %}
  <div>
    <pre>{{answer.displayed_proof[0]}}<div class="erroneous-line">{{answer.displayed_proof[1]}}</div>{{answer.displayed_proof[2]}}</pre>
  </div>
    <p class="mistake-message">{{answer.displayed_message}}</p>
  {% endif %}
</div>